Piston



Sept. 3, 1935. H. B. CHAFFIN 2,012,956

PISTON Filed March 25, 1954 s Sheets-Sheet 1 -1 INVENTOR:

- ATTORNEYS.

Sept. 3, 1935, H. B. CHAFFIN 4 2,012,955

PISTON I Filed March 25, 1954 3 Sheets-Sheet 2 flu? 16 1 I 17dWITNESSES: INVENTOR:

% 50 71211 95. am n Patented Sept. 3, 1935 UNITED STATES PATENT OFFICEThis invention relates to pistons; and it has reference moreparticularly to piston construction for steam locomotive engines.

In steam locomotives it has been the general practice heretofore toemploy bull rings-in association with the pistons to hold the lattercentralized in the cylinders, as well as separate packing rings tomaintain a fluid-tight working seal with the cylinder walls. I am awarethat attempts.

have been made heretofore to dispense with the bull rings, and to devisepackings which would serve both as a centering and sealing means. Theproposed combination bull and packing rings were, however,unsatisfactory from the standpoint of complicity of parts, difiiculty inassembling, and unreliability for the maintenance of a satisfactory sealdue to excessive wear upon the cylinder through development of loosenessbetween the component ring parts and the piston.

The chief aim of my invention is to overcome the drawbacks which havebeen pointed out, or in other words, to afford a combined bull andpacking ring which is simple in construction as regards the number ofits component parts, and which can be depended upon for fluid tightnessover long periods of service as a consequence of strict confinement ofthe ring parts to radial movement relative to the piston.

Other objects and attendant advantages will 'be manifest from thefollowing detailed description of the accompanyingdrawings; wherein,Fig. I shows the face view of a steam locomotive pis- ,ton convenientlyembodying the combined bull and packing ring of my invention.

Fig. II is a fragmentary detail view, on a larger scale, showing theouter surface of the ring in linear development.

Fig. III is a fragmentary detail cross sectional view of the ring, takenas indicated by the arrows III-III in Fig. I, and drawn to a largerscale.

Figs. IV and V are views corresponding to Figs. II and III, showing amodified form of my inventlon; and,

Figs. VI, VII and VIII, IX are views, also corresponding respectively toFigs. H and III, showing further modifications of my invention. I

With detailed reference first more particularly to Figs. 1-111 of theseillustrations, the numeral I0 designates the piston which has 'arelatively broad peripheral portion ll integrally joined by 'acontinuous dished web I2 with a central boss or hub l3. As-shown in Fig.III the piston l0 formed with a. pair of laterally-spaced rectangularsection circumferential grooves ltwhereof the depth is considerablygreater than the width.

. In order to hold the piston Ill centered in the engine cylinder and atthe same time insure a fiuid tight working joint between it andthe,cylinder wall l5 (Fig. III), .in accordance with my invention I haveprovided a combined bull-andpacking ring which, as will be observed fromFigs. I and II, is composed of a number of interchangeable arcuatesegments IE, "5.1:. The segment 16w which lies at the bottom or" the,piston lo has an arcuate length exactly twice that of the others,

and, by virtue of its position, supports most of the weight of saidpiston. As best shown in Fig. III, the combined bull-and-packing ringhas a face portion I! which is substantially as wide as the .piston I 0,and which overlies the periphery of said piston, thereby filling thespace between the piston periphery and the cylinder wall IS with itsouter surface l8 bearing full, against said cylinder wall I5. Thecombined bull-and-packing ring moreover has internally thereof, a pairof laterally-spaced circumferential ridges l9 which are rectangular incross section and proportioned to snugly fit within, and tosubstantially fill circumferential grooves l4 of the piston II]. A pairof split, round section, annular expander springs 20 engaginginwardly-open central grooves 2| in the ridges l9, urge the ringsegments I6 uniformly outward into intimate fluid-tight contact with thecylinder wall l5, and also assist in maintaining said segmentsaccurately in circumferential alignment. For the better lubrication ofthe piston II], the combined bull-and-packing ring isformed with oilgrooves Z! in its outer face I8, said oil grooves being respectively oncenter with the ribs or ridges l9, as shown in Fig. III.- At

opposite ends, the ring segments I6 are rabbatted, as at 23 in Fig. II,for overlapping-engagement and the formation of fluid-tight workingjoints between them, the longitudinal faces -24 of said joints being inthis instance allaligned in the central plane of the ring.

Due to the integral formation of the ring segments l6, Ilia: with tworidges l9 proportioned as above described, the force-of the lateralthrust imposed upon thering bysteam pressure acting on the piston III,will obviously be communicated to; and proportionately absorbed by thewalls of the grooves M in said piston. Furthermore, since the contactingareas of the ridges l9 and the sides of the grooves [4 are relativelylarge and well spaced laterally, the ring segments I6, I 6:: arestrictly confined to radial movement, with consequcnt efiectiveminimization of wear in the piston groves I4 and preclusion of anyrelative rocking movement which would cause rapid wear between the ringand the cylinder wall I5, and result in steam leakage past the pistonIII as was the case with the single ridge rings heretofore usuallyemployed in the art. A further advantage of the 8 above construction isthat the radial thrust of ingly held against the cylinder wall I5b formainthe combined bull-and-packing ring is evenly distributed by thejoint action of the two split annular expander springs 20, so that auniform pressure is maintained between the outer face of the ringsegments I6, I61: and the cylinder wall I5 all around.

In the embodiment of my invention illustrated in Figs. IV and V, thepiston Illa. is formed with three rectangular section circumferentialgrooves Ila, and the combined bull-and-paclring ring with acorresponding number of ridges I 9:: to engage the piston grooves Ila.The companion segments I6a of the ring overlap at their ends in the samemanner as before; but it will be noted from Fig. IV that, in this case,the longitudinal lap faces 24a of successive joints 22a, arerespectively in line with the opposite faces of the central one of theridges I911. This construction avoids splits medially of the groove I lafor the central expander spring 20a. Except as above noted, the modifiedconstruction of Figs. IV and V is similar in its design and operation tothat of the first described embodiment, and therefore, in order topreclude the necessity for repetitive description, the same referencenumerals have been employed to designate corresponding parts, theexponent it having however been additionally applied in each instancefor the purpose of distinction.

In Figs. VI and VII, I have illustrated a combined bull-and-packing ringfor a piston I 0b having three circumferential grooves I lb. In thisinstance, the segments I6b of the ring have registering end recesses 25which jointly provide spaces for the reception oi snugly-fittingsupplemental segments 26 to lap the junctures 23b between the abuttingfaces of the main segments. Each supplemental segment 26, it will beobserved from Fig. VII, has a segmental ridge 21 to engage the centralone of the three circumferential grooves Ilb in the piston I 0b; whileeach main segment l6b has three ridges I9b-,to engage all of the pistongrooves Mb. Due to their allocation medially of the piston assemblage,the supplemental segments 26 are subject to the central one of the threeexpander springs 20b, which latter collectively. exert their influenceupon the main segments l6b so that all the components of the combinedbull-and-packing ring. are yieldtenance of a fluid tight working seal.

Figs. VIII and IX show my invention embodied in a piston I60 having fourcircumferential grooves Ila. Here, the main segments I6 0 of thecombined bull-and-packing ring are recessed at their corners as at 28,with resultant provision of spaces along opposite side edges of thepiston lie \for the reception of snugly-fitting supplemental segments26c to lap the juncturoshc between the abutting end faces of contiguousmain segments I6c. In this modification, the single ridges 21c of thesupplementalsegments 260 along the opposite side edges of the pistonllc, respectively engage the outermost ones of the circumferentialgrooves llc, whereas the main segments I60 each have four ridges Me toengage all of the circumferential piston grooves Ilc. As shown inFig. DIthe supplemental segments I6c are influenced by the outermost ones ofthe four expander rings 26c, which latter all operate in common upon themain segments I6c to keep them yieldingly in fluid-tight contact withthe cylinder wall I6c.

The alternative forms of my invention featured in Figs. VI, V11 andVIII, IX are advantageous in that they favor more economicalconstruction of the combined bull-and-packing ring, since the mainsegments I6?) and I60 can all be cut from a preformed annular machinedblank without wastage except for that occasioned by the end recesses at25 or 28. The ring segments for the forms of my invention shown in Figs.I, III and IV, V, on the other hand, obviously cannot all be producedfrom a single annular blank on account of the offset formation oftheiropposite ends.

From the foregoing it is evident that I have provided a combinedbull-and-packing ring which is composed of relatively few parts; whichis easily and quickly assembled; which is likewise easily and quicklyintroduced into the cylinder initially,

as well as readily withdrawn from the cylinder when replacement becomesnecessary; which is self lubricating; and which can be relied upon tomaintain an efllcient fluid-tight seal between the piston and thecylinder wall over along period of service.

Having thus described my invention, I claim:

1. The combination with a piston having a number of laterally-spacedrectangular section circumferential grooves in its periphery; of acombined bull-and-packing ring having a face portion correspondingsubstantially in width to, and overlapping the periphery of the piston,said ring being composed of overlapping arcuate segments jointlyproviding a plurality of laterally spaced rectangular sectioncircumferential internal ridges to snugly fit the circumferentialgrooves of the' piston, each said ridge having an inwardlyopen groove,and annular expander means engaged in such grooves to yieldinglymaintain the ring segments in fluidtight contact with a cylinder wall.

2. The combination with a piston having a number of laterally-spacedrectangular-section circumferential grooves in its periphery of a depth.in excess of their width; of a combined bull-andpacking ring having aface portion corresponding substantially in width to, and overlappingthe periphery of the piston, said ring being composed of overlappingarcuate segments jointly providing a plurality of laterally-spacedrectangular section internal ridges of rectangular cross sectionproportioned to fit snugly into and to substantially fill thecircumferential grooves of the piston, the respective ridges each havingan inwardly-open groove, and an expander ring in each of the grooves toyieldingly maintain the ring' segments in fluid tight contact with acylinder wall.

3. The combination with a piston haying'a number of laterally-spacedrectangular-section circumferential grooves in its periphery; of acombined bull-and-packingring having a face portion correspondingsubstantially in width to, and overlying the periphery of the piston,said ring being composed of overlapping arcuate segments Jointlyproviding internal laterally-spaced rectangular section circumferentialridges to snugly fit the circumferential grooves of the pis-,.

segments into fluid tight contact with a cylinder wall.

4. A piston in accordance with clalm'twbcrein II the piston has anuneven number of groovesand the combined bull-and-packing ring acorrespondform with the longitudinal surface contact at opposite ends ofthe-ring components lying in the planes of the opposite sides of thecentral one of the ridges aforesaid. x

5. A piston for horizontal cylinders in accordance with claim 1 whereinthe lowermost arcuate segment of the circumferential series is ofgreater arcuateextent than the others for capacity to better support themajor part of the weight of the piston.

6. The combination with a piston having a number of laterally-spacedrectangular section circumferential grooves in its periphery; of acombined bull-and-packing ring having a face portion correspondingsubstantially in width to, and overlapping the periphery of the piston,said ring being composed of a number of abutting main segments, and anumber of supplemental segments to overlap the cross wise junoturesbetween the main segments, said main and supplemental segments jointlyproviding laterally-spaced rectangular section circumferential internalridges to snugly fit the circumferential grooves of the pistons, therespective-ridges each having an inwardly-open groove, and a splitexpander ring in each of the grooves to yieldingly maintain all the ringsegments in fluid tight contact with the cylinder wallf HARRY B.CHAFFIN.

